Various filters have been employed to remove at least some impurities from water or wastewater. Prior filters include but are not limited to upflow filters or upflow clarifiers, downflow filters and bi-flow filters. Typically, filters include a filter bed with one or more layers of granular media. During a filtration cycle or service run, influent (i.e., liquid to be filtered) is directed through the filter bed to remove impurities from influent. Various devices have been used to direct influent through the filter bed and collect effluent (i.e., filtered liquid). For example, underdrains formed from a plurality of laterals have been used below the filter bed in upflow filters and upflow clarifiers to direct influent through the filter bed. One or more layers of gravel have been used to support one or more layers of filter media above the underdrain laterals. Porous plates operably connected to each of the plurality of underdrain laterals have been used to support one or more layers of filter media in the filter bed above the underdrain laterals to eliminate the need for gravel support layers. Alternatively, underdrains having a plurality of nozzles arranged below the filter bed have been used in upflow filters and upflow clarifiers to direct influent through the filter bed during a filtration cycle or service run. In downflow filters or clarifiers, underdrains are used to collect effluent. Underdrains are also used in both upflow filters and downflow filters during periodic cleaning cycles to direct a washing liquid through the filter bed to remove impurities trapped in the filter bed during a filtration cycle. To assist in the cleaning of filter beds air may be directed through the filter bed during a cleaning cycle. The cleaning cycle can include several phases including but not limited to liquid only, liquid and air concurrently and air only.
U.S. Pat. Nos. 5,534,202 and 5,673,481 disclose, inter alia, a known method of inserting an air grid into a filter bed to assist in cleaning of the filter bed. Specifically, these patents disclose fluidizing the filter bed to permit insertion of the air grid in the filter bed without removing filter media from the filter bed. While this was a significant improvement over prior systems, there are instances where fluidization of the filter bed is not practical and/or possible. One aspect of a preferred embodiment of the present invention is to use a vibrator to insert an air grid into a filter bed without fluidizing the filter bed and without removing filter media from the filter bed. Regardless of the manner in which media in the filter bed is agitated to permit a fluid distribution system to be inserted at least partially in the filter bed without removing media, it is important that the fluid distribution system be able to be installed during agitation of the filter bed without one or more individuals located directly above the filter bed to guide the fluid distribution system to an operating position. For example, where the media is fluidized to install the fluid distribution system, liquid passing through the filter bed can create a safety hazard for individuals that are positioned above the filter bed to guide the fluid distribution system into an operating position. Therefore, one aspect of a preferred embodiment of the present invention is to provide a fluid distribution system that eliminates the need for one or more individuals to be positioned above the filter bed to guide the fluid distribution system into an operating position. Again, regardless of the manner in which the filter bed is agitated to permit the fluid distribution, it is important that the fluid distribution system be properly oriented when installed. The agitation of the filter media during installation can cause the fluid distribution system to be improperly oriented when installed. This is particularly true where the fluid distribution system is large. Hence, another aspect of a preferred embodiment of the present invention is to provide a fluid distribution system that can be readily installed in an orientation that optimizes the effectiveness of the fluid distribution system. Drop pipes are used in fluid distribution systems to supply a washing fluid to other elements of the fluid distribution systems including one or more headers and a plurality of laterals operably associated with the one or more headers. If the drop pipe has a crack or other defect, influent during the filtration cycle can enter the drop pipe and pass downwardly through the filter without traveling through the filter bed. This is referred to as short circuiting of the filter bed. A further aspect of a preferred embodiment of the present invention is to provide a fluid distribution system that eliminates or significantly reduces short circuiting of the filter bed. Yet a further aspect of a preferred form of the present invention is to provide a fluid distribution system that readily informs an operator of the presence of liquid in one or more drop pipes signaling a defect in the drop pipe that could result in short circuiting of the filter bed.
Where air scour systems are used to assist in cleaning of the filter bed, it is typical for components of the air scour system including but not limited to drop pipes to at least partially fill with liquid when the air scour system is not operating to direct air through the filter bed. This is undesirable as the liquid must be evacuated from the air scour system when the air scour system is employed to direct air through the filter bed. Another aspect of the preferred embodiment of the present invention is directed to a fluid distribution system configured to prevent one or more components of the air scour system from filling with liquid.